VYPR
← All advisories
Medium severity5.5NVD Advisory· Published May 17, 2024· Updated May 12, 2026

CVE-2024-35807

CVE-2024-35807

Description

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix corruption during on-line resize

We observed a corruption during on-line resize of a file system that is larger than 16 TiB with 4k block size. With having more then 2^32 blocks resize_inode is turned off by default by mke2fs. The issue can be reproduced on a smaller file system for convenience by explicitly turning off resize_inode. An on-line resize across an 8 GiB boundary (the size of a meta block group in this setup) then leads to a corruption:

dev=/dev/<some_dev> # should be >= 16 GiB mkdir -p /corruption /sbin/mke2fs -t ext4 -b 4096 -O ^resize_inode $dev $((2 * 221 - 215)) mount -t ext4 $dev /corruption

dd if=/dev/zero bs=4096 of=/corruption/test count=$((2*2**21 - 4*2**15)) sha1sum /corruption/test # 79d2658b39dcfd77274e435b0934028adafaab11 /corruption/test

/sbin/resize2fs $dev $((2*2**21)) # drop page cache to force reload the block from disk echo 1 > /proc/sys/vm/drop_caches

sha1sum /corruption/test # 3c2abc63cbf1a94c9e6977e0fbd72cd832c4d5c3 /corruption/test

2^21 = 2^15*2^6 equals 8 GiB whereof 2^15 is the number of blocks per block group and 2^6 are the number of block groups that make a meta block group.

The last checksum might be different depending on how the file is laid out across the physical blocks. The actual corruption occurs at physical block 63*2^15 = 2064384 which would be the location of the backup of the meta block group's block descriptor. During the on-line resize the file system will be converted to meta_bg starting at s_first_meta_bg which is 2 in the example - meaning all block groups after 16 GiB. However, in ext4_flex_group_add we might add block groups that are not part of the first meta block group yet. In the reproducer we achieved this by substracting the size of a whole block group from the point where the meta block group would start. This must be considered when updating the backup block group descriptors to follow the non-meta_bg layout. The fix is to add a test whether the group to add is already part of the meta block group or not.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

A flaw in ext4 on-line resize can cause filesystem corruption when crossing meta block group boundaries, affecting systems with large ext4 filesystems (≥16 TiB).

Vulnerability

Overview

CVE-2024-35807 describes a corruption bug in the ext4 filesystem driver in the Linux kernel, triggered during an on-line (online) resize operation. The issue occurs when a filesystem larger than 16 TiB with 4k block size (or smaller filesystems with resize_inode disabled) is grown across an 8 GiB meta block group boundary. The ext4 driver incorrectly updates the backup block group descriptors, leading to persistent disk corruption that can be verified via checksum mismatches after a cache drop [1][2].

Attack

Vector and Prerequisites

Exploitation requires local access to a system where the adversary can trigger an on-line resize of an ext4 filesystem that spans a meta block group boundary. No special privileges beyond the ability to issue resize2fs (often root) are needed, but the system must have an ext4 filesystem meeting the size or configuration requirements. The corruption manifests after the resize and a subsequent cache eviction, causing data read from disk to differ from what was written [1][2].

Impact

Successful exploitation results in silent data corruption on the affected ext4 filesystem. Files that were written before the resize may later be read back with incorrect content, as demonstrated by a reproducible checksum change after the resize + drop_caches sequence. This compromises filesystem integrity and can lead to application errors or data loss [1][2].

Mitigation

The Linux kernel upstream has addressed this vulnerability. The fixed commit is included in stable kernel updates; users should apply the latest updates from their distribution. For systems where the bug is triggered, affected filesystems should be checked and repaired with fsck. There is no workaround other than avoiding on-line resizes across meta block group boundaries on unpatched kernels [3][4].

References
  1. SSA-398330
  2. SSA-265688
  3. Making sure you're not a bot!
  4. Making sure you're not a bot!

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

154

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

13

News mentions

0

No linked articles in our index yet.